documentclass{article}

usepackage[citestyle=authoryear, bibstyle=alphabetic, natbib, backend=bibtex]{biblatex}
usepackage{filecontents}

begin{filecontents}{jobname.bib}
@misc{whatever,
  author = {Author, A.},
  year = {2001},
  title = {Testing the effects of biblatex styles on bibliography formatting},
}

end{filecontents}

addbibresource{jobname.bib}

begin{document}
citep{whatever}
printbibliography

end{document}

FUNCTION {makelabel:alpha:year} {
  dateyear purify
  #1  #4 substring$
  #1  #4 substring$
}